An almanac’s tables are computed once, carefully, and then consulted all year — nobody recomputes them from memory at each consultation, because a table re-derived by mood is wrong in a different place every time. A character kept on an ephemeris card gets the same discipline. Described fresh at every job, she is re-tabled each time, and every re-tabling moves her a little. Written once and clipped into the almanac, she is simply consulted.
The card holds five entries in fixed order. Age, a plain number. Hair — colour, length, one habitual style. Build in two or three words. Face — one or two enduring details. Signature — the detail that survives a tight crop. Beneath the entries, the sitting line for the day: outfit, setting, hour, light. The sitting line is expected to change; the table is not.
Paste the card word for word at the head of every prompt. Generate at the standard cost of 6 credits, keep the best third, and judge every result against the table — not against the previous frame, which may itself have drifted off it.
Drift is not a model problem. It is a records problem. Keep the table computed once, and the character holds her place in it.